One thing you won't find on your TV is a commercial for cigarettes, and it's one of the few "broadcasting" issues on which the federal government and Hollywood have common ground. While smoking remains legal for adults, it's off limits to children, and cigarette advertising would decidedly entice youngsters to dabble in that vice.

It's a simple, cause-and-effect argument.

In that vein, it should not be surprising that Rebecca Collins and a team of researchers at the RAND Corporation have discovered a similar pattern for prime-time television's nearly omnipresent patter about sex, sex, sex. It's only natural that children might be swayed by the idea that if their TV idols not only talk about sex a lot, but also engage in sex a lot, they should, too. In a study for the journal Pediatrics, Collins reports that heavy exposure to sexual content on television related strongly to teenagers' initiation of intercourse or their progression to more advanced sexual activities (such as "making out" or oral sex) apart from intercourse in the following year.

Young people who viewed the greatest amounts of sexual content were two times more likely than those who viewed the smallest amount to initiate sexual intercourse during the following year or to progress to more-advanced levels of other sexual activity. Collins found that teens who watched the most sexual content "acted older." A 12-year-old at the highest levels of exposure behaved like a 14- or 15-year-old at the lowest levels.

Collins underscored the obvious: Television is now a big part of social learning, working like the maxim "monkey see, monkey do. If everyone's talking about sex or having it, and something bad hardly ever comes out of it, because it doesn't on TV, then they think, 'Hey, the whole world's doing it, and I need to.'"

One of the most troubling findings showed that talk about sex on TV had virtually the same effect on teen behavior as depictions of sexual activity. That's a big departure from the widespread belief that rarer portrayals of action have a more powerful impact than the nightly barrage of sex chatter.

Public health experts dislike this state of the culture because sitcoms stress sex without the consequences -- sexually transmitted diseases, pregnancy and even depression among sexually active teenagers. Anyone guided by moral principles bemoans the sorry state of an amoral, relativistic society where sinful behavior is not only condoned, it's encouraged.

So what's the solution? Again, a simple truth.

Collins found that the most powerful countervailing influence on teen sexual activity is, unsurprisingly, parental involvement. Having parents who monitored their teen's activities, having parents who were more educated or who were clearly disapproving of teenagers having sexual relations, and teens living with both parents were all strong indicators of delayed sexual activity.

But if parents are the solution, they not the root problem. It is the producers of the raunch who are most responsible.

And yet it's also not a surprise that Hollywood did not want to take one iota of responsibility for the behavior for what their ever-saucier attempts to grab audience actually do to people after the TV is turned off. They fully expect that the young viewer goes out and buys Starburst fruit chews and eats at McDonald's after watching the ads on television, but if they are influenced to have sex after seeing it on television, the tube couldn't possibly be the cause. "With all due respect to RAND, we do not believe that one show can alter a person's sexual behavior," huffed Jeff Cusson, a spokesman for HBO, the horny home base of "Sex and the City."

That's one tired Hollywood line. The other is a dodge: It's up to parents, not us. "Some TV may be too provocative for kids, but that doesn't mean it shouldn't be on the air," claimed Todd Leavitt, president of the Academy of Television Arts and Sciences. "As the father of three daughters, I believe parents have an obligation to monitor their kids' TV viewing."

The Hollywood logic is inescapably empty. Let's drop the age limits for alcohol consumption and say it's up to parents to stop teens from hitting the bars. Why the need for driver's licenses? Parents should monitor this, too.

And while we're at it, let's resuscitate those Joe Camel tobacco ads and plaster them on TV, since television isn't responsible for influencing behavior.